Insulating material.



J. U. DOW.

INSULATING MATERIAL.

APPLICATION FILED JULY 5. 1907.

952,51 3. Patented Mar. 22, 1910.

i z I I 4 III/II/IIIIJ WITNESSES: lNVENTOR 6 V3 X7 2 BY \V. v 1 J ATTORNEY UNITED STATES PATENT oFFioE.

JAMES C. DOW, F WILKINSBURG, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

INSULATING MATERIAL,

Specification of Letters Patent. Patented B131. 22, 1910..

Application filed July 5, 1907. Serial No. 382,390.

To all whom 'it may concern:

were omitted from the structure. The

Be it known that 1, JAMES C. Dow, a citiamount of surface leakage is also materially zen of the United States, and a resident of VVilkinsbur r, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Insulating Materials, of which the following is a specification. D

My invention relates to insulators for high-potential electrical circuits, and it has for itsobject to provide an insulating body in which the. strains will be prevented from concentration upon or adjacent to outer surfaces but will be distributed throughout the thickness of the body.

The invention consists in constructing an insulator of alternate layers of suitable insulating and conducting materials, a series of condensers being thereby provided between the external surfaces of the insulator whereby the total strain to which the insulator is subjected is distributed throughout the thickness of the insulating material.

The single figure of the accompanying drawing is a view, partially in elevation-and partially in section, of an insulating bushing that embodies my invention.

In the drawing, a rod or bar 1 of anysuitable conducting material, which may con-. stitute a circuit lead, is provided with an insulating bushing 2 by which it is insulated from a metal casing or supporting bracket 3. The insulating bushing 2 is preferably constructed as set forthin Patent No. 858,385, granted July 2, 1907, to the \Vestinghouse Electric & Manufacturing Company, as assignee of Emil Haefely, sheets 4 of tinfoil or other suitable conducting material being interposed at convenient or desired intervals between the convolutions 5 of insulating material during the construction of the bushing.

The metallic sheets 4 form with each other and with the conductor 1 a series of condensers in which the strains upon the insulation are proportional to the differences of potential between the sheets. The strain upon the insulating bushing is, therefore, distributed throughout its thickness and is not concentrated upon its inner surface, as has heretofore been the case. The thickness of the bushing, for a given strain, may, therefore, be materially reduced over what would be necessary if the metallic sheets reduced by means of this structure.

The best results may be secured by so constructing the insulating bushing that the condensers which constitutethe series may be of equal capacities, and if the condenser plates are of substantially equal areas the most economical and compact product may be obtained.

I claim as my invention:

1.- An insulating bushing comprising a plurality of continuous convolutions of suitable insulating material, and separate convolutions of conducting material interposed 'in the bushing at intervals;

2. An insulating body comprising convolutions of sheet insulating material and convolutions of sheet conducting material between adjacent insulating convolutions.

3. An insulating body comprising a series of condensers having conducting layers of substantially equal areas and separating insulating layers of substantially equal thicknesses.

4. An insulating bushing comprising a plurality of substantially concentric metal cylinders and separating insulating cylinders, the metal cylinders being of equal areas and the insulating cylinders of equal thicknesses.

5. An insulating bushing comprising substantially concentric metal and insulating cylinders of unequal lengths which are alternately disposed to constitute a series of condensers.

6. An insulating'bushing comprising sub stantially concentric metal cylinders of graded lengths, the longer cylinders being within the shorter, and spacing insulating cylinders which cooperate with said metal cylinders to constitute a series of condensers.

7. An insulating body comprising a plurality of similar metallic members having substantially arallel surfaces and spacing insulating cylinders which cooperate therewith to constitute a series of condensers of equal capacities.

of substantially equal areas and interleaved metal cylinders and to make the areas there layers of insulation which ciiperate thereof substantially equal.

with to constitute a series of condensers. In testimony whereof, I have hereunto 10. An insulating bushing comprising a subscribed my name this 28th day of June,

plurality of equally spaced substantially 1907.

concentric metal cylinders and separating JAMES C. DOW.

insulating layers, the ends of said bushing Witnesses:

being tapered to increase the surface dis- R. J. DEARBORN,

tances between the ends of the adjacent BIRNEY H'INEs. 

